1. Field of the Invention
The present invention relates to a data recording/reproducing apparatus for properly performing an error correction code encoding process depending on whether a data recording medium is a recordable/reproducible type or a reproduction-only type, a method thereof, and a data recording medium.
2. Description of the Related Art
As external storing units for use with computers, from view points of large storage capacity and high access speed, optical disc drives are popular. CD-ROM (or CD-I (CD interactive)) drives and MO (magneto-optical disc) drives have been rapidly and widely used. An MO disc is one type of erasable discs. In addition, an MD (mini-disc) that is an erasable type disc has been proposed. Moreover, as a picture record medium, a DVD (digital video disc) is now under development.
The DVD is a reproduction-only disc with the same diameter as the diameter of the CD or a recordable/reproducible optical disc that is an MO type disc or a phase change type disc that reproduces or records/reproduces picture information compressed corresponding to the MPEG standard or the like. As well as the wavelength of laser rays decreases and the NA of an objective lens increases, the digital modulation and the error correction code encoding process have been improved, the recording density has been further improved. In the case that the DVD is a single layer type disc, the data storage capacity is as much as around 3.7 Gbytes. The CD and MD were originally developed for digital audio discs. Thereafter, these discs have been used for external storage mediums for computers. Likewise, the DVD with much larger storage capacity than the CD and MD is expected to be used for external storage medium for computers.
Data recording mediums such as optical discs can be categorized as a reproduction-type disc and a recordable/reproducible disc. In the recordable/reproducible disc, countermeasures against errors are performed by a data substituting process especially for computers. However, in the reproduction-only disc, since the data substituting process cannot be performed, a high error correction performance is required. In the reproduction-only disc, since data is continuously read, a relatively large sector size and a folding type encoding process can be used. However, in the recordable/reproducible disc on which data is randomly rewritten, data with a large sector size is not always continuously recorded on the disc. In addition, data should be unnecessarily reproduced for correcting errors. Thus, the throughput increases and the harmonization to the computers deteriorates.
Considering the difference in characteristics of the reproduction-only disc and the recordable/reproducible disc, dedicated error correction code encoding processes are performed for the reproduction-only disc and the recordable/reproducible disc. Thus, for these error correction code encoding process, dedicated algorithms for encoding and decoding processes are necessary. In addition, dedicated encoders and decoders must be designated for the error correction code encoding processes. Moreover, IC circuits for the encoder and decoder must be designed.